The present invention generally relates to wound dressings and, more particularly, to a highly absorbent hydrogel for use in wound dressing products which are particularly useful in the active therapy of thermal, chemical, electrical, and similar wounds conventionally classified as "burns."
Burn injuries require a unique combination of therapy and dressing because the physiologic functions of the skin are absent or, at best, materially impaired. Body fluids and their essential components are continuously lost. The natural barrier characteristics normally provided by one's skin, of preventing invasion of harmful micro-organisms and other noxious agents, are no longer functional. Potentially fatal infections are a continuous serious threat to burn patients. The debris reservoir of necrotic tissue saturated with seeping wound exudate remains on the wound site, harboring and nourishing agents of infection whose presence and by-products interfere with the regeneration of viable, functioning, epithelial tissue having skin organ properties.
The basic tenets of therapy required to treat burns are specifically directed toward providing and improving the impaired physiologic functions of the skin. Of initial concern is the removal of the necrotic products of injury. Also of great importance is providing a barrier to bacterial invasion from the environment while controlling the contamination already present. Finally, burn therapy is directed toward stemming the loss of vital body fluids.
Burn injuries and the like have been treated at various stages by application of sterile coverings in the form of pastes or creams, gauze wrappings, natural and synthetic membranes, films, or sponges. Except in the case of skin grafting, the approach has been to prevent adhesion of the covering materials to the wound site while encouraging adhesion of the burn exudate to the covering materials.
One existing burn exudate absorption method is to apply a polyurethane polymer composition to the burn site. As disclosed in Gould, U.S. Pat. No. 4,156,066, and Gould, U.S. Pat. No. 4,156,067, issued May 22, 1979, a polyurethane polyether resin may be applied to a burn as a powder. However, powder tends to attract fluids from the burn wound and deteriorates as the wound fluids are absorbed, resulting in lumping and uneven application. Additionally, such deteriorated lumps are difficult to remove from a burn site without damaging new cell tissue at the burn site.
A burn dressing which attempts to minimize fluid loss from the burn site is disclosed in U.S. Pat. No. 3,648,692, issued to Wheeler on Mar. 14, 1972. The Wheeler burn dressing discloses an open cell foam material which can be applied directly to a burn wound site. However, while it is desirable to stem the loss of vital body fluids from the already weakened patient, the Wheeler burn dressing eliminates or minimizes the loss of all fluids, even fluids contaminated with necrotic tissue, from the burn site. Also, new cell tissue forming at the burn site may adhere to the sponge-like material, making it difficult to remove the burn dressing from the burn site without damaging new cell tissue. Consequently, the Wheeler burn dressing serves merely as a sedentary covering for allowing the burn to heal, rather than actively expediting the healing.
Aqueous moisture absorbing materials, such as a polyethylene glycol liquid curing agent as disclosed in Spence, U.S. Pat. No. 4,226,232, issued Oct. 7, 1980, are easier to remove from the wound site, but cannot be sterilized by irradiation due to the formation of free radicals within the aqueous material. Another aqueous absorbing material used to absorb wound exudate, hydrophilic polymer, is disclosed in Rawlings et al, U.S. Pat. No. 4,657,006, issued Apr. 14, 1987. In the Rawlings et al reference, a wound dressing is described which comprises a hydrophilic polymer having moisture vapor permeability characteristics. A problem with the Rawlings et al wound dressing is that the wound exudate absorbed by the hydrophilic polymer hardens the polymer, allowing pockets to develop between the polymer and the wound, providing an excellent environment for bacteria proliferation.
Known aqueous moisture absorbing wound dressing systems have additional problems, in that the aqueous material is generally contained in the center portion of a wound dressing, with a bulky adhesive border, such as a foam border. Problems with such borders include decreased comfort, conformity and adhesion as well as the existence of a "lifting edge" that can catch on clothes or bed sheets, thereby exposing the wound to bacteria and infection. In addition, burn sites typically have very little healthy skin to which such a dressing may be adhered.
An existing method of overcoming the problems associated with bulky wound dressings is disclosed in Potts, U.S. Pat. No. 3,526,224 issued Sep. 1, 1970. The Potts reference discloses a wound dressing comprised of an elastomeric polyurethane film which acts as a second skin during the wound healing process. One problem with the Potts wound dressing, however, is that the "second skin" requires surgery to remove it after the wound has healed.
Hence, it would be desirable to provide a burn dressing which eliminates or minimizes vital and healthy fluid loss from a burn site while simultaneously removing contaminated or infected wound fluids. It would also be desirable to provide a burn dressing product which could be readily available for application to a burn wound. It would further be desirable to provide such a burn dressing which contains wound debridement characteristics and which absorbs large quantities of wound exudate yet does not adhere to the burn site, thereby providing means to expedite healing. In addition, it would be desirable to provide a burn dressing which could be removed neatly and, more importantly, without adhering to the new cell tissue forming at the burn site. Finally, it would be desirable to provide such a burn dressing product which could be comfortably applied to any area on a body.